Process for treating nylon yarns for knitting



M 5, 1969 H. D. SIERER 3,459,848

PROCESS FOR TREATING NYLON YARNS FOR KNITTING Filed Jan. 25, 1967 I NV ENTOR ax/a 0. 5/595? 3,459,848 PROCESS FOR TREATING NYLON YARNS FOR KNITTING Harry D. Sierer, Wilmington, DeL, assignor to E. I. do

Pout de Nemours and Company, Wilmington, Del., a

corporation of Delaware Filed Jan. 25, 1967, Ser. No. 611,620 Int. Cl. D01d 7/06; B29c 25/00 US. Cl. 264235 6 Claims ABSTRACT OF THE DISCLOSURE Freshly spun nylon yarn is drawn to a draw ratio of about 2.5 to about 3.5, annealed at substantially constant length at a temperature from about 125 C. to about 150 C. for a time of about 0.1 to about 0.5 second. The hot yarn is then allowed to relax from about 2% to about 3% and wound to a package. The process provides a method of preparing nylon yarn used in knitted fabric which is essentially free from edge curling.

This invention relates to the production of nylon yarns for use in knitted fabrics.

State of the art In US. Patent No. 2,956,330, G. Pitzl describes a process for producing a highly uniform nylon yarn of high modulus and low shrinkage, in which process the freshly drawn yarn is subjected to a partial anneal at constant length, and a partial relaxation. Although these yarns are very satisfactory for woven fabrics, under some finishing procedures used for knitted fabrics, the fabric has an undesirable tendency to curl at the edges.

Object It is therefore, an object of this invention to provide a process for drawing, setting, and relaxing nylon yarn which can be used to make knitted fabric essentially free edge curling.

Statement of invention This and other objects are attained in a process comprising the steps of:

(a) spinning nylon yarn (b) drawing the freshly spun yarn to a draw ration R (c) annealing the freshly drawn yarn at substantially constant length at a temperature T C. for a time of about 0.1 to about 0.5 second (d) allowing the hot yarn to relax from about 2 to about 3% (e) winding the yarn to a package The graph in the accompanying drawing shows the annealing temperature, at various levels of edge-curling propensity, as described more fully in the example.

Test methods Tricot fabric is knitted from the test yarn, and heat set. Tongues are produced by making six cuts, 1" apart, and 5" long, parallel to the selvedge edge of the heat set ted States Patent 0 "ice fabric which has been equilibrated for 2 hours at the specified humidity. The amount of curl is estimated visually on a scale of 1 (unacceptable) to 5 (perfect). A rating of 3 is considered marginally acceptable.

A numerical measurement of curling propensity of a test yarn is made by hanging a loop of the test yarn over a 0.035" diameter steel pin, under a load of 0.125 gm./den. The loaded loop on the pin is heat set for 1 minute at 320: 2 F., the sample is cooled and the top /2-%" of the loop is cut and dropped on a smooth surface. After lagging for 2 hours at the test humidity, the actute angle between the yarn ends is measured, giving a recovery angle. It is found that this single correlates linearly with the edge curl rating, an angle of 17.5 corresponding to a rating of 5, and an angle of 65 to a rating of 1.

Example 1 Polyhexamethylene adipamide yarn is extruded through a 13 hold spinnert, quenched and then drawn to various draw ratios. The drawn yarn passes in multiple wraps around a pair of draw rolls enclosed in a chest supplied with heated air. The chest temperature is also varied simultaneously in a statistically designed experiment. Yarn residence time in the hot chest is 0.18 sec. The hot yarn is allowed to retract (relax) 3% on its way to a surface driven zero twist windup. The curl rating of the test yarns is then determined.

The data obtained are plotted on a graph, and the boundary of the area required to give a curl rating of 4 or better is determined; the area is shown in the figure, as the shaded area within ABCD. Similarly, EFG bounds curl rating of 3.5 and HI], of 2.5. The minimum chest temperature is about C., since this temperature is required to set the yarn enough to get an acceptably low shrinkage.

The coordinates of area ABCD are given in the table below.

Processing variables Although the above relationships have been developed for an annealing chest heated with hot air, steam or inert gas may be used as a heat transfer medium. Alternatively, hot plates, heated tubes, radiant heat or inert fluid (oil or silicones) baths may be employed.

The yarn time in the hot chest may be increased by increasing the number of wraps on the rolls, or by decreasing yarn speed. Increase in time in the annealing zone will usually permit the use of lower temperatures for the same draw ratio.

Before entering the annealing oven, the yarn may be drawn in one, two, or more stages.

It will be understood that various changes in the details and steps, which have been described and illustrated herein in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

What is claimed is:

1. A process comprising:

(a) spinning a nylon yarn forming a freshly spun yarn (-b) drawing the said freshly spun yarn to a draw ratio of from about 2.5 to about 3.5 (c) annealing the said freshly spun drawn yarn at substantially constant length at a temperature of from about 125 to about 150 C. for a time of about 0.1 to about 0.5 second (d) allowing the hot yarn to relax from about 2 to about 3%. 2. The process of claim 1 wherein said yarn is wound to a package.

3. The process of claim 1 wherein said time is from about 0.16 to about 0.20 second.

4. The process of claim 1 wherein said draw ratio is about 2.7 and said temperature is about 140 C.

5. A process comprising: (a) Spinning a nylon yarn forming a freshly spun yarn (b) drawing the said freshly spun yarn to a draw ratio R (c) annealing the said freshly spun drawn yarn at substantially constant length at a temperature T 20 for a time of about 0.1 to about 0.5 second 4 (d) allowing the hot yarn to relax from about 2 to about 3%,

said draw ratio R and said temperature T being chosen so that the point defined by the coordinates of the said R and said T falls within the area under the curve ABCD in the appended drawing.

6. The process of claim 5 wherein said yarn is wound to a package.

References Cited UNITED STATES PATENTS 2,956,330 10/1960 Pitzl 264290 3,124,632 3/1964 Larkin et a1 264-290 3,311,691 3/1967 Good 264-290 DONALD J. ARNOLD, Primary Examiner J. H. WOO, Assistant Examiner US. Cl. X.R. 264210, 290, 345 

